Two-year study finds no brain benefit for fish oil

NEW YORK (Reuters Health) - Fish oil may be good for your heart, but it doesn't seem to help preserve your smarts, a new two-year study shows.

"This is an important finding because a lot of people are taking fish oil in the hopes that it will be good for their cognitive function," Dr. Alan D. Dangour of the London School of Hygiene and Tropical Medicine in the UK, one of the study's authors, told Reuters Health. But he didn't rule out the possibility that taking fish oil for a longer period of time might have beneficial effects.

Numerous studies have shown that people who eat more fish have better mental function, and are less likely to develop dementia. "The problem with a lot of these studies of course is there are lots of reasons why people eat more fish," Dangour pointed out.

To better answer the question of whether fish oil, in and of itself, benefits the brain, Dangour and his team randomly assigned 748 men and women in their 70s -- none of whom had any dementia or other impairment of mental function -- to take 200 milligrams of eicosapentaenoic acid (EPA) plus 300 mg docosahexaenoic acid (DHA) every day for two years or a placebo capsule containing olive oil. EPA and DHA are the two main omega-3 fatty acids found in fish oil.

Neither group showed any change in cognitive function over the 24-month trial, as measured by a battery of tests of mental function they took at the beginning and end of the study. The percentage of people who died or dropped out was similar in both groups.

"We can clearly say that after two years there's no evidence for a benefit" in terms of cognitive function, Dangour said. He and his colleagues note in their report that theirs is the largest and longest randomized controlled trial to date investigating omega-3s and mental function in older people.

This doesn't mean that people might benefit their brains by taking fish oil capsules for longer than two years, he added. But, he said, "There's no good evidence at the moment from randomized controlled trials that it's good for cognitive function."

SOURCE: American Journal of Clinical Nutrition, online April 21, 2010.